Both polyolefin (PO) and poly(phenylene ether) (PPE) have relatively low thermal and shear stabilities when they are used in pristine alone or in physical blends. PO as the most important commodity plastic typically sees viscosity changes when subjected at 120° C. or above use temperatures for a certain period of time as the result of molecular structure changes under thermal or thermo-oxidative conditions. By empirical definition, an engineering thermoplastic (ETP) can maintain mechanical and dimensional stability above 100° C. and below 0° C., and therefore can be used as light-weight and high-performance structural material, replacing metals, wood, glass, or ceramics. PPE as one of the important ETPs boasts excellent dimensional stability but the pristine PPE is intrinsically instable at high temperatures and under high shear rates. This instability is a result of its reactive chain end from the manufacturing process. The common industrial process to mitigate its instability is to cap the reactive chain end with other functional groups to reduce the reactivity. The chain end treated PPE would then desirably survive processing conditions and applications. However most known functional groups will come off at higher temperatures, which compromises PPE's other outstanding properties and limits its broader application as an ETP. What is needed is a way to improve the stability of PPE's so that they can be thermally formed into such articles as “under the hood” automotive components that require a high degree of thermal stability.